Biometric systems are gaining importance because they are more trustworthy and efficient for identity verification. Gait is one such biometric. The manner in which a person walks is referred to as gait. It is locomotion accomplished by the movement of a person's limbs. Unlike other methods, gait is a behavioural biometric that is considered for user authentication because it reveals unique patterns for each individual. In addition, the fact that this biometric technique is less intrusive to the user makes it superior to others. This survey focuses on various gait approaches, applications, and machine learning techniques that will be used for classifying gait characteristics and their applications